以計算探討鉑錫基催化劑在直接乙醇燃料電池陽極和陰極反應中的研究

Computational study of PtSn-based catalysts for anodic and cathodic reactions in direct ethanol fuel cells

顏劭晏(Yan Shao-Yan)

指導教授 ： 王禎翰

國立臺灣師範大學/理學院/化學系/碩士(2018年)

https://doi.org/10.6345/THE.NTNU.DC.014.2018.B05

摘要

本研究分陰極觸媒和陽極觸媒兩部分: PtSn雙金屬催化劑上的陰極氧還原反應（ORR）和陽極乙醇氧化反應（EOR）。在ORR的研究中，使用Pt（111）表面取代不同Sn比例來模擬PtSn催化劑。我們的計算發現，Sn取代越多，活性越高，這歸因於其較低的親氧性和相鄰Pt的d-band center；然而，越多的Sn由於結構扭曲降低穩定性。穩定性可以藉由錫氧化物修飾Pt表面進一步改善，在ORR過程中，這些氧化物對Pt表面吸附適中及強的斥力以保持結構。而在EOR的研究中，通過在PtSn中添加Ag形成三元PtSnAg催化劑來修飾PtSn雙金屬。Ag上的氧化物由於可以吸引解離的氫以及與OH有排斥效應可以有效改進關鍵步驟CH3CHO氧化成CH3COOH而促進了EOR。此外，氧化物可以增強乙醇在鄰近的Pt上的吸附以降低初始脫氫反應。

關鍵字

鉑錫催化劑 ； 鉑錫銀催化劑 ； 奈米線 ； 氧氣還原反應 ； 乙醇氧化反應 ； 偏析能 ； 態密度

並列摘要

The present study includes two main parts: the cathodic oxygen reduction reaction （ORR） and anodic ethanol oxidation reaction （EOR） on PtSn bimetallic catalysts. In the study of ORR, PtSn catalyst was modeled by Pt （111）surface with varied Sn substitution of surface Pt. Our calculations found that the more Sn substitution results the higher activity, attributable to their lower oxophilicity and d-band center of adjacent Pt; however, the more Sn substitution demotes the stability due to the structural distortion. The durability can be further improved by separating and lifting the oxide phase of Sn on Pt surface. The oxide has moderate adsorption on Pt surface and strong repulsion among them to retain the structure during ORR. In the study of EOR, we modified PtSn bimetal with the addition of Ag forming ternary PtSnAg catalyst. The oxide phase of Ag can effectively enhance CH3CHO oxidize to CH3COOH, the key step, and promote EOR activity due to its attraction of dissociated H and repulsion of OH. Additionally, the oxide can assist ethanol adsorption on the neighboring Pt that can lower the initial dehydrogenation step.

並列關鍵字

PtSn catalyst ； PtSnAg catalyst ； nanowires ； oxygen reduction reaction(ORR) ； ethanol oxidation reaction(EOR) ； segregation energy ； density of states(DOS)

參考文獻

1. Liu, C.-Y. and C.-C. Sung, A review of the performance and analysis of proton exchange membrane fuel cell membrane electrode assemblies. Journal of Power Sources, 2012. 220: p. 348-353.

2. Sharma, S. and B.G. Pollet, Support materials for PEMFC and DMFC electrocatalysts—A review. Journal of Power Sources, 2012. 208: p. 96-119.

3. Garraín, D., Y. Lechón, and C.d.l. Rúa, Polymer Electrolyte Membrane Fuel Cells （PEMFC） in Automotive Applications: Environmental Relevance of the Manufacturing Stage. Smart Grid and Renewable Energy, 2011. 02（02）: p. 68-74.

4. Holton, O.T. and J.W. Stevenson, The Role of Platinum in Proton Exchange Membrane Fuel Cells. Platinum Metals Review, 2013. 57（4）: p. 259-271.

5. Samjeske, G., et al., Performance and characterization of a Pt-Sn（oxidized）/C cathode catalyst with a SnO2-decorated Pt3Sn nanostructure for oxygen reduction reaction in a polymer electrolyte fuel cell. Phys Chem Chem Phys, 2013. 15（40）: p. 17208-18.